Interest in prediction resulted in a shift of emphasis
from the depiction and explanation of geographical
patterns to that of process identification to understanding
the dynamics of regional economies and the
nature of human spatial behavior. Thus, from a
fundamental focus on pure spatial form, attention
turned to the movements of objects and to the passage
of events through space and time. Models to simulate
urban growth and other phenomena as processes of
spatial diffusion (see Diffusion: Geographical Aspects)
(represent explicit attempts to mesh the time and space
dimensions in geographical research. Significant
statements advancing time–space perspectives are
found in Ha$gerstrand’s (1973) conceptualizations
of spatial diffusion and time-geography, Janelle’s
(1969) formulation of time–space convergence,
and Harvey’s (1990) notion of time–space compression.